Circular??? Linear???

[Dishman Dan]

Last night I was aiming my motorized "ChinaMaster" 1M with a Invacom LNBF that I bought off of Ebay quite some time ago. I aimed for my true south at 87 degrees but ended up on the 91 bird which has Bell programming. I am using one of the linear ports on the Invacom and nothing is hooked to circular. It seems strange to me that when I blind scanned, the receiver showed like 300 encrypted channels are on the 91. I thought that Bell was circular and I am not sure why it even locked on those channels! Is Bell circular or linear??? Is my Invacom going nutz???

 

[SatelliteAV]

Bell is circular.

A linear LNBF can pick-up circular signals with approximately 3dB attenuation.

 

[turbosat]

DD, you didn't say what receiver, apparently your scan continued on past the usual 12200 mhz, shouldn't have grabbed those circular tps otherwise. I have one or two old boxes that will scan to 12900 if I don't watch them and hit the Exit button at 12200. Can really load up the channel list in a hurry!

 

[Dishman Dan]

Bell is circular.

A linear LNBF can pick-up circular signals with approximately 3dB attenuation.

Thanks!

I did not know that and I had no idea what was up!!!

 

[Dishman Dan]

DD, you didn't say what receiver, apparently your scan continued on past the usual 12200 mhz, shouldn't have grabbed those circular tps otherwise. I have one or two old boxes that will scan to 12900 if I don't watch them and hit the Exit button at 12200. Can really load up the channel list in a hurry!

I had a Coolsat 6000 hooked up while tweaking the dish and I will go check what the settings were. I have a Pansat 3500SD that I use more but it never picked up circular.

 

[eurosport]

Bell is circular.

A linear LNBF can pick-up circular signals with approximately 3dB attenuation.

Yup. I had the same problem. I have a 1.0m P* with original H/V LNB, pointed at 91w, and after the first time I always choose "FTA" on a blind scan of this bird, so all the DBS stuff doesn't show up. It still finds the transponders but won't load 300 useless channels.

 

[trommy]

91 has a lot of linear feeds.

 

[Tron]

My Invacom picks up E* stuff from the linear side anytime I'm within 2 degrees of 119w... It is frustrating, as it will quickly load your channel and TP lists up with useless info.

 

[Mikey11]

if you can set your TP limits/range for your blind scan then set it to 11700 - 12200....this will stop the scan before it gets into the circular frequencies....

either that or just manually stop the scan when it hits 12200....normally you can do this by pressing the "exit" button....

 

[Mr Tony]

My old Pansat always would go to 12350 so I would get those DBS frequencies too

Thank goodness the GeosatPro and Coolsat stops at 12200

 

[B.J.]

With my 3' dish, I usually pick up the first transponder, like 12224, but rarely pick up the other ones, because there is too much interferrence since the circular signals are overlapping on both sides. When I tune a BUD with linear Ku and a polarotor for polarity, to those DBS sats, I can usually play with the polarity a bit and lock the other transponders.
But anyway, I've never had that problem of picking up hundreds of DBS channels when using an LNBF that doesn't have adjustable polarity. I usually only scan in the first one for some reason, which I always assumed was because it only had interferrence on one side.
Interesting that other people are picking up all these transponders.

 

[Dishman Dan]

With my 3' dish, I usually pick up the first transponder, like 12224, but rarely pick up the other ones, because there is too much interferrence since the circular signals are overlapping on both sides. When I tune a BUD with linear Ku and a polarotor for polarity, to those DBS sats, I can usually play with the polarity a bit and lock the other transponders.
But anyway, I've never had that problem of picking up hundreds of DBS channels when using an LNBF that doesn't have adjustable polarity. I usually only scan in the first one for some reason, which I always assumed was because it only had interferrence on one side.
Interesting that other people are picking up all these transponders.

So this "interference" could be a design fluke in the Invacom quad???

If I install a simple straight out linear Ku LNBF I could avoid this clutter???

I used to scan Ku with my BUD but I am setting this up (finally) because the

winter brings lake effect snow which knocks the Ku out on the BUD way too

often!

 

[SatelliteAV]

This is not a fluke. You are simply scanning above 12.2GHz (IF 1450) with your receiver. If you can adjust the Blind Scan End/Stop frequency to 12200 (or IF frequency 1450), you will not scan these undesired channels.

 

[Dishman Dan]

This is not a fluke. You are simply scanning above 12.2GHz (IF 1450) with your receiver. If you can adjust the Blind Scan End/Stop frequency to 12200 (or IF frequency 1450), you will not scan these undesired channels.

Thanks

When I get a chance to finish up tuning, I will double check my settings. It has

been all work and no play lately. I should of had everything installed and

setup long time ago.

 

[B.J.]

So this "interference" could be a design fluke in the Invacom quad???

If I install a simple straight out linear Ku LNBF I could avoid this clutter???

I used to scan Ku with my BUD but I am setting this up (finally) because the

winter brings lake effect snow which knocks the Ku out on the BUD way too

often!

I agree with Sat-Av's response, but to clarify my reference to "interference", I was referring to the fact that a linear feed receives R and L circular equally well, so if my receiver tries to tune 12239L on linear, it is also receiving 12224R and 12253R, which interfere a bit with it, which I think is why I generally DON'T scan those channels in, while I generally DO scan in the 12224R, which only has the 12239L interferring. So the interferrence I was referring to was with respect to my NOT getting those unwanted channels, not having anything to do with WHY other people ARE getting those channels, which Sat-Av explained.
BTW, with the blind scan receivers I've used, it's several more keystrokes to tell it to stop at 12200, so I always just let it continue on, but I was never bothered by many additional channels. I don't think I had an option to change the default stop value, ie I'd have to do it each time I scanned. That was with a couple Fortec receivers. I generally rarely use blind scan anymore, so it isn't an issue.